- The sample size calculation was based on the pilot study developed by Mira et al. (2015) whereas the use of the TENS for relief of chronic pelvic pain and deep dyspareunia generated by endometriosis, whose pre-and post-treatment discomfort was assessed by Visual analog scale (EVA). The number of women in this study was of 22 women divided into two treatment groups. Applied for the calculation of sample size, the t test for independent variables to the study cited and given a power of test 90% and significance level of 5%, the sample size obtained was of 24 patients in total. Considering the following loss of 20%, the total number shall be 29 women, divided into two groups: follow-up/treatment group (n = 15) and treatment/monitoring group (n = 14). For better quantification of all the variables involved, we will seek ideally a total of 80 women, divided into two groups (n = 40).